Rrh Ramon Schiffelers

Application of Supervisory Control Synthesis to a Patient Support Table of a Magnetic Resonance Imaging Scanner

In this paper, we present a case-study on application of Ramadge-Wonham supervisory control theory (abbreviated by SCT in the sequel) to a patient support system of a magnetic resonance imaging (MRI) scanner. We discuss the whole developmental cycle, starting from the mathematical models of the uncontrolled system and of the control requirements, and ending with the implementation of the obtained controller on the actual hardware. The obtained controller was tested on the physical system. In this case study, we attempted to build the models in a modular way, in order to decrease the computational complexity of the controller synthesis and to improve the adaptability of the models. An important advantage of SCT is that it allows automatic generation of the controller, and that it can thus improve adaptability of the control software. We also briefly discuss our experience on the adaptability of the control software, obtained in the course of this case study.

Model-based Engineering of Embedded Systems Using the Hybrid Process Algebra Chi

Hybrid Chi is a process algebra for the modeling and analysis of hybrid systems. It enables modular specification of hybrid systems by means of a large set of atomic statements and operators for combining these. For the efficient implementation of simulators and the verification of properties of hybrid systems it is convenient to have a model that uses a more restricted part of the syntax of hybrid Chi. To that purpose the linearization of a reasonably expressive, relevant subset of the Chi language is discussed. A linearization algorithm that transforms any specification from this subset into a so-called normal form is presented. The algorithm is applied to a bottle-filling line example to demonstrate tool-based verification of Chi models.

Assessing and improving quality of QVTo model transformations

Abstract We investigate quality improvement in QVT operational mappings (QVTo) model transformations, one of the languages defined in the OMG standard on model-to-model transformations. Two research questions are addressed. First, how can we assess quality of QVTo model transformations? Second, how can we develop higher-quality QVTo transformations? To address the first question, we utilize a bottom–up approach, starting with a broad exploratory study including QVTo expert interviews, a review of existing material, and introspection. We then formalize QVTo transformation quality into a QVTo quality model. The quality model is validated through a survey of a broader group of QVTo developers. We find that although many quality properties recognized as important for QVTo do have counterparts in general purpose languages, a number of them are specific to QVTo or model transformation languages. To address the second research question, we leverage the quality model to identify developer support tooling for QVTo. We then implemented and evaluated one of the tools, namely a code test coverage tool. In designing the tool, code coverage criteria for QVTo model transformations are also identified. The primary contributions of this paper are a QVTo quality model relevant to QVTo practitioners and an open-source code coverage tool already usable by QVTo transformation developers. Secondary contributions are a bottom–up approach to building a quality model, a validation approach leveraging developer perceptions to evaluate quality properties, code test coverage criteria for QVTo, and numerous directions for future research and tooling related to QVTo quality.

Fast Multiprocessor Scheduling with Fixed Task Binding of Large Scale Industrial Cyber Physical Systems

Latest trends in embedded platform architectures show a steady shift from high frequency single core platforms to lower-frequency but highly-parallel execution platforms. Scheduling applications with stringent latency requirements on such multiprocessor platforms is challenging. Our work is motivated by the scheduling challenges faced by ASML, the worlds leading provider of wafer scanners. A wafer scanner is a complex cyber-physical system that manipulates silicon wafers with extreme accuracy at high throughput. Typical control applications of the wafer scanner consist of thousands of precedence-constrained tasks with latency requirements. Machines are customized so that precise characteristics of the control applications to be scheduled and the execution platform are only known during machine start-up. This results in large-scale scheduling problems that need to be solved during start-up of the machine under a strict timing constraint on the schedule delivery time. This paper introduces a fast and scalable static-order scheduling approach for applications with stringent latency requirements and a fixed binding on multiprocessor platforms. It uses a heuristic that makes scheduling decisions based on a new metric to find feasible schedules that meet timing requirements as quickly as possible and it is shown to be scalable to very large task graphs. The computation of this metric exploits the binding information of the application. The approach will be incorporated into the ASMLs latest generation of wafer scanners.

A semantic-preserving transformation from the compositional interchange format to UPPAAL

Abstract The Compositional Interchange Format (CIF), is a modeling formalism for hybrid systems, that aims to establishing interoperability of a wide range of tools by means of model transformations to and from CIF. UPPAAL is a very successful tool for the specification and analysis of timed systems. It is interesting, both from a theoretical and a practical perspective, to be able to translate CIF models to UPPAAL models, since this makes it possible to model check properties of timed CIF models. This requires a semantic preserving transformation, which ensures that properties validated in UPPAAL models also hold for their CIF counterparts. In addition, by providing such a translation we are, at the same time, providing translations for a wider set of languages that can be transformed to CIF. This paper presents a semantic-preserving transformation from a subset of CIF models to UPPAAL. The transformation described in this work constitutes the cornerstone for transformations of a broader subset of CIF.

A Transformation Framework for the Compositional Interchange Format for Hybrid Systems

Abstract The purpose of the Compositional Interchange Format for hybrid systems (CIF) is to establish inter-operability of a wide range of tools by means of model transformations – using the CIF as intermediate, the implementation of many bi-lateral translators between specific formalisms can be avoided. This paper presents the architecture of the CIF transformation framework. Languages in the CIF transformation framework are defined by means of conceptual models, and transformations are specified by means of transformation languages. To avoid large monolithic transformations, transformations are divided into many small single- or cross-formalism transformations, each with their own concern. In this way, transformations are obtained that are easier to understand and can be re-used individually. A domain-specific language ToolDef has been developed to specify complex, automated tool chains that are based on these small individual transformations. The ToolDef architecture is illustrated using a translation between the CIF and UPPAAL, and an example for the application of the transformation framework is given based on a transformation between the CIF and gPROMS.

Modular model-based supervisory controller design for wafer logistics in lithography machines

Development of high-level supervisory controllers is an important challenge in the design of high-tech systems. It has become a significant issue due to increased complexity, combined with demands for verified quality, time to market, ease of development, and integration of new functionality. To deal with these challenges, model-based engineering approaches are suggested as a cost-effective way to support easy adaptation, validation, synthesis, and verification of controllers. This paper presents an industrial case study on modular design of a supervisory controller for wafer logistics in lithography machines. The uncontrolled system and control requirements are modeled independently in a modular way, using small, loosely coupled and minimally restrictive extended finite automata. The multiparty synchronization mechanism that is part of the specification formalism provides clear advantages in terms of modularity, traceability, and adaptability of the model. We show that being able to refer to variables and states of automata in guard expressions and state-based requirements, enabled by the use of extended finite automata, provides concise models. Additionally, we show how modular synthesis allows construction of local supervisors that ensure safety of parts of the system, since monolithic synthesis is not feasible for our industrial case.

Robustness analysis of multiprocessor schedules

Tasks executing on general purpose multiprocessor platforms exhibit variations in their execution times. As such, there is a need to explicitly consider robustness, i.e., tolerance to these fluctuations. This work aims to quantify the robustness of schedules of directed acyclic graphs (DAGs) on multiprocessors by defining probabilistic robustness metrics and to present a new approach to perform robustness analysis to obtain these metrics. Stochastic execution times of tasks are used to compute completion time distributions which are then used to compute the metrics. To overcome the difficulties involved with the max operation on distributions, a new curve fitting approach is presented using which we can derive a distribution from a combination of analytical and limited simulation based results. The approach has been validated on schedules of time-critical applications in ASML wafer scanners.

Deriving simulators for hybrid Chi models

The hybrid Chi language is a formalism for modeling, simulation and verification of hybrid systems. The formal semantics of hybrid Chi allows the definition of provably correct implementations for simulation, verification and real-time control. This paper discusses the principles of deriving an implementation for simulation and verification directly from the semantics, and presents an implementation based on a symbolic solver. The simulator is illustrated by means of a case study.

Maintenance of specification models in industry using Edapt

Domain specific languages (DSLs) ease the adoption of formal specification in industry. They allow developers to describe their specification models in concepts of their domain. However, DSLs evolve over time, causing specification models to have to co-evolve to reflect the evolution in the DSL. The maintenance overhead introduced by these, often manual, changes to specification models threatens to overshadow the advantages of DSL usage in industry. To this extent, many approaches have been proposed in the literature to facilitate DSL maintenance by automating model co-changes. In this paper, we evaluate the ability of a tool, Edapt, to support the change and co-change in twenty-two industrial DSLs and corresponding specification models over a maintenance period of four years. We observe that the tool is only able to automatically co-change specification models for 72% of the DSL changes. To address the remaining 28% of the changes, we extend Edapt. The resulting extension allows automatically co-changing specification models for 98% of the DSL changes.